xref: /aosp_15_r20/external/libvpx/vpx_ports/aarch32_cpudetect.c (revision fb1b10ab9aebc7c7068eedab379b749d7e3900be)

/*
 *  Copyright (c) 2023 The WebM project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */
// Feature detection code for Armv7-A / AArch32.

#include "./vpx_config.h"
#include "arm_cpudetect.h"

#if !CONFIG_RUNTIME_CPU_DETECT

static int arm_get_cpu_caps(void) {
  // This function should actually be a no-op. There is no way to adjust any of
  // these because the RTCD tables do not exist: the functions are called
  // statically.
  int flags = 0;
#if HAVE_NEON
  flags |= HAS_NEON;
#endif  // HAVE_NEON
  return flags;
}

#elif defined(_MSC_VER)  // end !CONFIG_RUNTIME_CPU_DETECT

static int arm_get_cpu_caps(void) {
  int flags = 0;
#if HAVE_NEON || HAVE_NEON_ASM
  // MSVC has no inline __asm support for Arm, but it does let you __emit
  // instructions via their assembled hex code.
  // All of these instructions should be essentially nops.
  __try {
    // VORR q0,q0,q0
    __emit(0xF2200150);
    flags |= HAS_NEON;
  } __except (GetExceptionCode() == EXCEPTION_ILLEGAL_INSTRUCTION) {
    // Ignore exception.
  }
#endif  // HAVE_NEON || HAVE_NEON_ASM
  return flags;
}

#elif defined(VPX_USE_ANDROID_CPU_FEATURES)

static int arm_get_cpu_caps(void) {
  int flags = 0;
#if HAVE_NEON || HAVE_NEON_ASM
  uint64_t features = android_getCpuFeatures();
  if (features & ANDROID_CPU_ARM_FEATURE_NEON) {
    flags |= HAS_NEON;
  }
#endif  // HAVE_NEON || HAVE_NEON_ASM
  return flags;
}

#elif defined(__linux__)  // end defined(VPX_USE_ANDROID_CPU_FEATURES)

#include <sys/auxv.h>

// Define hwcap values ourselves: building with an old auxv header where these
// hwcap values are not defined should not prevent features from being enabled.
#define VPX_AARCH32_HWCAP_NEON (1 << 12)

static int arm_get_cpu_caps(void) {
  int flags = 0;
  unsigned long hwcap = getauxval(AT_HWCAP);
#if HAVE_NEON || HAVE_NEON_ASM
  if (hwcap & VPX_AARCH32_HWCAP_NEON) {
    flags |= HAS_NEON;
  }
#endif  // HAVE_NEON || HAVE_NEON_ASM
  return flags;
}
#else   // end __linux__
#error \
    "Runtime CPU detection selected, but no CPU detection method available" \
"for your platform. Rerun configure with --disable-runtime-cpu-detect."
#endif

int arm_cpu_caps(void) {
  int flags = 0;
  if (arm_cpu_env_flags(&flags)) {
    return flags;
  }
  return arm_get_cpu_caps() & arm_cpu_env_mask();
}